THE  EFFECT  OF  DEOXIDIZING  AGENTS  ON 
THE  PHYSICAL  PROPERTIES  OF 
STEEL  CASTINGS 


BY 


HUGO  CHRISTIAN  LARSON 

A.B.  Augustana  College,  1919 

L 


THESIS 

SUBMITTED  IN  PARTIAL  FULFILLMENT  OF  THE  REQUIREMENTS 
FOR  THE  DEGREE  OF  MASTER  OF  SCIENCE  IN  CHEMISTRY 
IN  THE  GRADUATE  SCHOOL  OF  THE  UNIVERSITY 
OF  ILLINOIS,  1922 


URBANA,  ILLINOIS 


\ J (A. 


UNIVERSITY  OF  ILLINOIS 

THE  GRADUATE  SCHOOL 

MAY-3L, -IQ2-2 

I HEREBY  RECOMMEND  THAI'  THE  THESIS  PREPARED  UNDER  MY 


SUPERVISION  BY HTTCf)  CHRISTIAN  LARSON 

ENTITLED THE  EFFECT  OF  DEOXIDIZING  AGENTS  OR — 

THE  -PHYSICAL  PROPERTIES  _QF_STEEL  CAST LEGS 


BE  ACCEPTED  AS  FULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR 
THE  DEGREE  OF  IMS  TER  OF  SCIENCE  TN  CHEMTSTRY 


7±bb 


w. 


( -JJ. 


In  Charge  of  Thesis 


o<_a_a_ 


(JL-C.'tt  Ci  Head  of  Department 


Recommendation  concurred  in* 


Committee 

on 

Final  Examination* 


•Required  for  doctor’s  degree  but  not  for  master’s 


; ' '•  • • 


ACKNOWLEDGEMENT 

The  writer  wishes  to  express  his  most  sincere  appreciation  to 
Dr.  W.  S.  Putnam,  whose  personal  assistance  and  encouragement  were 
invaluable  during  this  investigation.  He  wishes  also  to  acknow- 
ledge  his  indebtedness  to  Professor  C.  W.  Parmelee  for  his  work  in 
connection  with  the  preparation  of  an  electric  furnace  and  zircon 
crucibles,  and  to  Mr.  E.  Sunstrom  for  his  kindness  in  preparing 
drawings  and  photographs  of  the  apparatus  used. 


• : f ; : u 


: 1 ' 


TABLE  OP  CONTENTS 


Page 

I.  Introduction  1 

II.  Historical  and  Theoretical  3 

III.  Apparatus  and  Experimental  6 

Purnaces  6 

Crucibles 16 

Slags 18 

Molds 19 

IV.  Summary 26 

V.  Bibliography 27 

VI.  Figures  

I.  Oil  furnace 7 

II.  First  type  of  furnace 9 

III.  Burner  with  air  preheater 11 

IV.  Pinal  type  of  furnace 13 

V.  Photographs  of  furnace 14 

VI.  Muffle  furnace  for  slag  melting  point 

determinations  20 

VII.  Types  of  molds 21 

VII.  Tables 

I.  Analysis  of  gas 12 

II.  Analysis  of  Flue  15 

III.  Calculation  of  slags 22,23 


Digitized  by  the  Internet  Archive 
in  2016 


https://archive.org/details/effectofdeoxidizOOIars 


THE  EFFECT  OF  DEOXIDIZING  AGENTS  ON  THE 
PHYSICAL  PROPERTIES  OF  STEEL  CASTINGS 

I 

INTRODUCTION 

Although  deoxidizing  agents  have  been  employed  successfully  in 
the  metallurgy  of  iron  and  steel,  the  effect  which  such  agents  have 
on  the  physical  properties  of  steel  castings  is  not  found  to  any 
great  extent  in  literature. 

This  problem  was  suggested  by  the  following  statement  of 
Giolitti^in  regard  to  the  special  methods  of  melting,  pouring, 
deoxidation  and  heat  treatment;  "An  explanation  in  great  detail  is 
at  present  impossible,  owing  to  the  fact  that  they  have  been  brought 
to  their  present  perfection  in  very  recent  times,  and  are  still 
held  as  industrial  secrets  only  partly  protected  by  patents."  (p£42) 
The  purpose  of  this  investigation  will  be  to  note  the  variation  in 
tensile  strength,  hardness,  ductility  and  crystalline  structure  with 
varying  amounts  of  the  ferro-alloy  of  the  less  common  deoxidizing 
agents,  such  as  vanadium,  titanium,  and  uranium.  The  steel  used  wiU 
be  forty  carbon  (o.40$  C)  and  will  be  cast  into  bars  of  sufficient 
size  to  be  machined  down  for  use  in  the  tensile  strength  testing 
machine.  The  hardness  will  be  determined  by  the  Brine 11  method  and 
micro -photographs  will  demonstrate  the  structure.  The  length  of 
time  of  heating,  the  percentages  of  deoxidizer  added,  the  length  of 
time  of  addition  before  pouring  and  the  temperature  of  pouring  are 
variables  which  will  be  controlled. 

The  castings  will  be  uniformally  heat  treated  according  to  the 
methods  suggested  by  Giolitti  for  the  treatment  of  soft  and 


. 


' 


. 


■■ 


-2- 


medium  carbon  steel. 


-3- 


II 

HISTORICAL  AND  THEORETICAL 

The  use  of  deoxidizing  agents,  or  "Scavengers”,  in  removing 

oxides,  nitrides  and  occluded  gases  dates  as  far  hack  as  the  Bessemer 

process  for  making  steel.  In  the  year  1856,  Sir  Henry  Bessemer  pub- 

( B ) 

lished  his  epoch-making  paper  in  which  he  called  attention  to  the 

necessity  of  manganese  as  an  addition  product  in  the  final  purifica- 

( 2 ) 

tion  of  the  steel.  Shortly  afterwards,  Yalton  , director  of  the 
Terre-Noire  Steelworks,  gave  an  explanation  of  the  part  manganese 
played  as  a deoxidizer  in  the  Bessemer  process,  and  in  1876,  Gautier 
(3)  communicated  to  the  Iron  and  Steel  Institute  the  value  of  ferro- 
manganese in  the  open-hearth  process.  Some  years  prior  to  Gautier, 
Siemens  called  attention  to  the  action  of  manganese  on  steel.  In 
1875,  Pourcel  manufactured  f erro -mangane se  in  the  blast  furnace. 
Robert s-Ansten  concluded  an  address  to  the  Iron  and  Steel  Institute 
in  1900^)  with  the  remark:  "May  we  not  hope  that  in  the  next  century 
vanadium,  molybdenum,  titanium  and  glucinium  will  prove  as  faithful 
allies  as  manganese?" 

As  early  as  1894,  Rossi ^ observed  the  beneficial  effect  of 
titanium  in  the  manufacture  of  steel,  and  the  ferro-alloy  of  that 
element  was  studied  by  Wohler  and  St.  Clair  Devilled)  about  the 

/ c \ 

same  time.  Vanadium  was  discovered  in  1830  by  Sef stronr  but  it 

was  not  until  1896  that  Chambley^)  showed  the  advantages  of  vanadium 
in  steel-making.  Aluminum/  8 ^ , cerium/9!  uranium,  molybdenum  and 
glucinium  have  all  been  used  as  deoxidizers  with  various  degrees  of 
success.  In  practice,  the  steel  is  first  partially  deoxidized  by 
f erro -manganese  or  spiegeleisen,  and  this  is  followed  by  addition  of 


: • 


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.5*  - 


If  ■ 


-4- 


the  ferro-alloy  of  vanadium,  titanium  or  uranium.  In  this  way,  all 
the  impurities  which  have  been  acted  upon  by  the  manganese  compounds 
are  removed  by  the  more  active  deoxidizers. 

Various  theories  have  been  advanced  to  explain  the  effect  of 

( 7 ) 

these  agents  on  steel.  Arnold  and  others  believe  that  the  bene- 
ficial effect  is  due  to  the  deoxidizing  or  ’’scavenger"  action  of  the 
substance.  Norris^11 ^ contends  that  the  improvement  of  physical  prop- 
erties is  due  to  the  fact  that  they  alloy  themselves  with  the  iron 

( 12 ) 

and  form  troostitic  and  sorbitic  pearlite.  Anderson  states  that 
besides  acting  as  deoxidizers,  they  tend  to  render  slags  more  fluid, 
causing  them  to  separate  more  completely  from  the  metal.  The  pres- 
ence of  the  oxide  of  titanium  or  vanadium  lowers  the  fusion  point  of 
the  occluded  slags  in  the  metal,  thereby  imparting  fluidity.  It  has 
been  found ^ 13 ^ that  6-§"$  of  Ti0  lowers  the  melting  point  to  1290°0.  and 
13$  addition  lowered  it  to  1190°C.  The  great  affinity  of  these  agents 
for  oxygen  is  a sure  means  of  reducing  the  occluded  oxides  such  as 
PeO,  PegOg,  and  such  gases  as  oxygen,  nitrogen  and  carbon  monoxide. 
The  fact  that  titanium  and  vanadium  unite  readily  with  nitrogen  make 
them  valuable  in  removing  that  element  from  the  metal.  The  harmful 
effect  of  nitrogen  on  iron  and  steel  was  brought  out  by  LeGhatelieJ*^ 
in  a paper  before  the  Congress  of  Metallurgists  in  Belgium  in  1905. 

He  showed  that  nitrogen  to  the  extent  of  from  .02  to  .045  percent  is 
sufficient  to  make  the  steel  so  brittle  that  elongation  and  reduction 
of  area  is  decreased  to  a marked  extent.  A great  increase  in  nitro- 
gen will  cause  the  steel  to  become  so  brittle  that  it  can  be  crumpled 
in  the  fingers.  Another  beneficial  effect  of  deoxidizers  is  their 

(15) 

tendency  to  retard  the  segregation  of  sulphur,  phosphorus  and  carbon. 

Very  little  of  work  done  by  metallurgists  in  studying  the 


-5- 

problem  of  deoxidation  has  been  concerned  with  steel  castings,  but 
the  theoretical  considerations  involved  are  practically  the  same. 

The  metallurgists  in  charge  of  the  steel-working  in  the  munition 
factories  of  several  European  countries  have  succeeded  in  making 
large  steel-castings  which  have  proved  to  be  just  as  resistant  to  the 

great  strains  they  must  bear  as  those  which  are  made  by  tedious  ma- 

f 16 ) 

chinery  and  forging.  The  Guldsmedshytte  Company,  Ltd. , in  Sweden, 
make  guns,  anchors  and  other  large  castings  of  cast  steel.  The  Gio. 
Ansaldo  Company  of  Italy  manufacture  large  steel  castings  for  gun- 
carriage  and  gun-mount  parts.  The  metallurgist  at  this  plant, 

F.  Giolattil^7)  states  that  this  was  accomplished  by  "obtaining  per- 
fect deoxidation  of  the  metal,  and  the  highest  possible  elimination  o: 
emulsified  non-metallic  inclusions  which  possess  an  oxidizing  power 
upon  the  mass  of  steel.  This  was  due  in  part  to  the  specific  action 
of  the  titanium  and  vanadium  used  in  their  manufacture  which  caused 
a great  frequency  of  the  centers  of  alpha  crystallization  which  form 
in  austenite  during  allotropie  transformation."  The  heat  treatment 
given  these  castings  by  Giolitti  is  another  important  factor  which 
helped  to  produce  a strong,  tough  steel  with  uniform  and  homogeneous 
crystalline  structure  throughout  the  material. 


-6- 

III 

APPARATUS  AND  EXPERIMENTAL 

In  the  attempt  to  solve  the  problem  of  the  effect  of  certain 

agents  on  steel  castings,  it  was  necessary  to  secure  homogeneous 

castings  of  40-carbon  steel  with  certain  percentages  of  the  various 

agents  added.  This  necessitated  a temperature  sufficiently  high,  not 

only  to  melt  the  steel  but  also  to  bring  it  about  100°C.  above  its 

melting  point  in  order  that  the  steel  would  not  solidify  during  the 

( 18 ) 

pour.  The  melting  point  of  the  steel  used  is  about  1425°C,  and 
it  was  thought  that  a temperature  of  1600°  would  be  high  enough  to 
secure  a pour.  It  has  been  stated/\that  the  longer  the  metal  is  kept 
in  the  furnace  in  the  liquid  state  and  the  higher  the  temperature  of 
the  pour,  the  greater  will  be  the  purification  accomplished. 

Furnaces:  The  first  furnace  used  was  an  oil-blast  furnace 
(See  FIG.  1)  After  several  attempts,  the  hope  of  obtaining  a good 
pour  from  this  furnace  was  abandoned,  because  the  highest  temperature 
reached  was  1450°C.  So  much  heat  was  lost  by  radiation  during  the 
removal  of  the  crucible  from  the  furnace  that  the  steel  was  left  in  a 
pasty  condition  which  made  it  impossible  to  pour. 

To  obtain  a higher  temperature,  gas  was  used  as  fuel  and  various 
types  of  furnaces  were  developed.  At  first,  a small  gas-air  blast 
furnace  was  tried,  but  the  highest  temperature  reached  in  this  type 
was  only  1350°C.  Preheating  the  gas  and  air  in  an  iron  tube  over  a 
series  of  Bunsen  burners  raised  the  temperature  to  1375°,  a tempera- 
ture at  which  the  steel  was  slightly  softened,  altho  still  in  the 
solid  state.  The  walls  of  the  furnace  were  constructed  of  a fire- 
clay refractory  only  two  inches  thick,  and  this  caused  such  a great 


• 

m 

-7- 


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-8- 


loss  of  heat  by  radiation  that  the  temperature  could  not  be  brought 
up  to  the  melting  point  of  the  steel.  An  additional  heat  insulator 
was  built  up  by  constructing  a sheet-iron  cylinder  around  the  furnace 
and  filling  this  with  pbwdered  silocel  made  into  a paste  with  water. 
When  this  was  dried  slowly,  all  the  water  was  expelled  leaving  a 
porous  insulating  wall  about  two  inches  thick  which  surrounded  the 
smaller  furnace.  This  prevented  the  loss  of  heat  to  a great  extent, 
and  on  a trial  run,  the  temperature  registered  about  1,400°C.  The 
silocel  insulator  melted  down,  however,  and  fire-clay  bricks  held 
together  with  alundum  cement  were  substituted.  (FIG?.  2) 

It  was  thought  that  the  preheating  of  the  gas  caased  an  expan- 
sion which  decreased  the  actual  quantity  of  gas,  and  so  the  air  alone 
was  pre-heated.  It  was  found  by  running  a blank  test  on  the  heating- 
value  of  the  preheated  air,  that  the  temperature  was  raised  300°0. 
This  was  sufficient  to  raise  the  temperature  the  necessary  amount 
above  that  due  to  the  gas  to  produce  a melt.  A few  trials  were  made 
by  passing  the  gas  thru  a cylinder  containing  naphthalene,  the  idea 
being  to  enrich  the  gas  with  a hydrocarbon  of  high  heat  value.  Out 
of  five  trials,  only  one  was  successful,  which  indicated  the  addition 
of  naphthalene  did  not  insure  high  temperatures,  but  rather  that  the 
variable  pressure  of  the  gas  from  the  mains  was  responsible  for  the 
failure  of  the  attempts.  It  was  found  that  the  greatest  heat  was 
obtained  between  9 and  11  P.M. , on  account  of  the  increased  pressure 
of  the  gas  at  that  time. 

An  oxygen  tank  was  connected  into  the  air-passage  in  such  a way 
that  the  air  could  be  enriched  with  varying  quantities  of  oxygen, 
thus  providing  for  the  complete  combustion  of  the  gas.  This  was  found 
to  supply  more  oxygen  than  was  necessary  for  the  burning  of  the  gas. 


-9- 


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-10- 


and  as  a result  the  oxidizing  atmosphere  caused  burning  and  disin- 
tegration of  the  graphite  crucibles. 

In  all  these  early  efforts,  the  gas  and  air-pipes  were  connectec 
to  the  valves  in  the  laboratory,  the  apertures  of  which  were  only 
3/16  inches  in  diameter.  These  small  openings  prevented  a large 
volume  of  gas  from  being  burned,  and  therefore  prevented  the  heat 
from  being  built  up  more  quickly  than  it  could  be  radiated  from  the 
outer  surface.  To  cbviate  this  condition,  a system  of  pipes  and  valves 
was  installed,  in  which  the  smallest  opening  was  inch  in  diamdter. 

A burner  was  also  constructed  with  an  air-chamber  made  of  1 inch  pipe 
surrounding  a ^ inch  gas-pipe,  and  extending  about  £ inches  beyond  the 
end  of  the  gas  pipe.  (See  FIG.  3-A)  By  this  means,  it  was  found 
that  temperatures  ranging  slightly  above  1,500  degrees  C.  could  be 
obtained. 

As  will  be  noted  in  FIG.  E,  the  gas  entering  at  a high  velocity 
strikes  the  crucible,  separates  on  either  side,  and  leaves  the  com- 
bustion chamber  thru  the  aperture  in  the  corner  of  the  furnace.  At 
the  high  temperature  of  the  furnace,  the  impact  of  the  gas  caused  the 
disintegration  of  the  crucibles.  This  took  place  so  rapidly  that  in 
several  runs,  the  crucibles  collapsed  in  the  furnace,  causing  the 
molten  metal  to  flow  out  into  the  furnace  chamber.  To  remedy  this, 
a furnace  was  constructed  of  firebrick,  lined  with  alundum  cement, 
with  the  burner  placed  on  one  side.  It  was  found  that  the  gas  re- 
bounded from  the  opposite  wall  and  did  not  heat  the  crucible  enough 
to  cause  the  steel  to  melt.  This  defect  was  remedied  by  rounding  the 
corners  of  the  furnace  and  the  gas  was  then  found  to  circulate  around 
the  crucible.  The  entrance  of  the  burner  into  the  furnace  was  too 

high,  which  prevented  the  bottom  of  the  crucible  from  being  heated. 


. 


-12- 


After  this  was  changed,  no  difficulty  was  experienced  in  obtaining 
a melt.  The  final  type  of  furnace  developed  is  shown  in  EIGJ.  4 and 
5. 

The  gas  used  thruout  the  work  was  ne%  furnished  by  the  C.  and  U 
Gas  and  Electric  Company  in  the  city  mains.  Upon  analysis  in  a modi- 
fied Orsat  apparatus'20^  it  showed  the  following  analysis: 


TABLE  I 

ANALYSIS  OF  GAS 


COMPOSITION 

PERCENTAGE 

ACCEPTED  HEAT 
VALUE 

■ 

TOTAL  HEAT  VALUE 

C2H4 

8.80 

1,588.0 

139.744 

QsHe 

0.20 

9,807.5 

7.614 

H2 

46.10 

326.2 

150.378 

CO 

20.00 

323.5 

64.700 

CH4 

6.13 

1,009.0 

61.852 

C2H6 

1.17 

1,764.5 

20 . 644 

co2 

5.70 

444 . 932 

Os 

1.00 

(B.t.u.  per 

n2 

10.90 

cu . f t ) 

100.00 

r\ 


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-15- 


By  means  of  a tube  and  a gas-sampling  apparatus,  two  liters  of 
exhaust  gas  was  withdrawn  and  analyzed.  The  low  percentage  of  carbon 
monoxide  and  the  slight  excess  of  oxygen  indicate  that  nearly  all  the 
heat  value  of  the  gas  was  being  obtained.  (See  TABLE  II) 


TABLE  II 

ANALYSIS  OP  FLUE  GAS 


COMPOSITION 

PERCENTAGE 

C02 

8.0 

CO 

0.5 

02 

5.0 

% 

86.5 

It  was  planned  to  use  an  electrical  resistance  furnace  for  melt- 
ing the  steel,  but  owing  to  difficulties  experienced  by  the  Department 
of  Ceramics,  this  was  not  completed  until  the  latter  part  of  the  term. 
En  the  first  trial  run,  it  was  found  that  a temperature  of  900°C.  was 
obtained  in  nine  minutes.  The  carbon  electrodes  became  heated  to  such 
a ,n  extent  that  a system  of  cooling  was  necessary.  A copper  sleeve 
vas  cast, and  fastened  around  the  electrode,  and  water  circulated  thru 
It.  This  proved  quite  successful  and  a temperature  of  1,800°C.  was 
obtained  without  causing  much  oxidation  of  the  electrodes.  As  an  addi- 
tional protection  against  oxidation,  the  electrodes  were  covered  with 
alundum  cement.  Altho  this  prevented  oxidation,  it  reacted  to  some 

sxtent  with  the  electrode.  A silmenite  coating  was  tried  and  this 
proved  very  satisfactory.  The  furnace  consisted  of  two  rings  of 

Acheson  graphite  placed  about  six  inches  apart  and  insulated  from 


' 


-16- 


tha  air  by  two  walls  of  refractory  material.  The  first  layer  was 
one  inch  in  thickness  and  made  of  a very  high  heat-resisting  refrac- 
tory, so  as  to  protect  the  outer  layer  which  consists  of  a 4 <§■  inch 
wall.  The  crucible  was  imbedded  in  finely  powdered  graphite  between 
the  rings, and  the  temperature  is  raised  by  the  heat  developed  from 
the  resistance  offered  to  the  passage  of  the  current.  In  practice, 
the  current  was  started  at  45  amperes  and  30  volts,  and  after  about 
30  minutes  this  was  stepped  up  to  95  amperes  and  40  volts.  (See  FIG  6 

Crucibles:  Considerable  difficulty  was  experienced  in  securing 

crucibles  which  would  withstand  the  high  temperatures  to  which  they 
were  subjected.  Dixon  graphite  crucibles  were  used,  but  these  did 
not  prove  very  successful  because  the  out  ear  surface  was  burned  con- 
siderably However,  when  a paste  of  alundum  cement  was  spread  over 
the  outer  surface  to  a thickness  of  \ inches,  this  was  prevented. 

The  basic  slags,  used  in  the  melt,  reacted  with  the  crucibles  and 
caused  their  decomposition.  When  an  alundum  cement  inner  lining  was 
tried,  it  was  found  that  the  basic  slag  reacted  with  the  alundum, 
forming  aluminates  which  went  into  the  slag.  Spinel  (magnesium  alum- 
inate)  was  mixed  with  a starch  paste  and s pread  on  the  inside  of  the 
crucible,  but  on  drying,  it  flaked  off  so  that  it  could  not  be  used 
as  a protective  casting  within  the  crucible.  By  the  use  of  an  acidie 
slag,  the  decomposition  of  the  crucible  was  avoided.  The  crucibles 
were  softened  by  the  heating  to  such  an  extent  that,  unless  the 
greatest  care  was  taken,  they  would  fall  to  pfejes  on  being  removed 

by  the  crucible  tongs. 

Some  ” zircon”  crucibles  were  prepared  under  the  direction  of 
Professor  Parmelee  of  the  Ceramics  Department.  They  were  made  of 


-18- 


zirconium  silicate  (ZrSiO^.),  and  contain,  therefore,  49.5$  zirconium, 
15.5 $ silicon  and  35$  oxygen.  The  melting  point  of  this  substance 
is  2 , 550°0 . { ^ ^which  is  sufficiently  high  to  warrent  its  use.  Two 
zircon  crucibles  were  filled  with  pieces  of  steel  and  slag  and  placed 
in  the  furnace  together  with  Segar  cones.  After  one  and  one -half 
hours  of  heating  in  which  the  highest  temperature  was  between  1,650 
and  1700°0S  they  were  found  to  have  softened  and  practically  dis- 
solved in  the  slag,  so  that  only  a few  particles  remained  unaffected. 
The  chemical  action  of  the  basic  slag  and  the  combination  with  the 
iron  were  probably  the  causes  of  their  complete  failure.  Later 
determinations  in  an  electric  furnace  (See  FIG.  6)  have  shown  that 
the  crucibles  do  not  melt  under  1800°C.,  when  free  from  impurities, 
but  they  are  very  much  affected  when  any  foreign  substance  is  placed 
in  them. 

Slags : The  melting  points  and  properties  of  various  combina- 

tions of  slags  were  determined  in  order  that  a suitable  slag  could 
be  found  for  the  purification  of  the  steel,  as  well  as  to  prevent 
atmospheric  oxidation.  The  oxides  used  in  forming  the  slags  were 
thoroly  mixed  and  ground  to  pass  a 100-mesh  screen.  Pyramids  of  the 
size  of  Segar  cones  were  formed  by  compressing  the  substance  into  a 
wood  mold.  Oil,  molasses  and  water  were  tried  as  binders,  the  first- 
mentioned  giving  the  best  results.  These  cones  were  dried  and  care- 
fully bales d in  a gas  muffle  at  about  1000 °C.  for  one  hour.  They  were 
then  placed  in  the  center  of  a gas  muffle  and  an  alundum  cement  rod 

was  rested  upon  the  point  of  the  cone.  The  rod  extended  thru  a hole 
in  the  top  of  the  muffle  in  such  a way  that  when  the  cone  melted 

the  rod  would  sink.  A platinum-platinum-rhodium  thermocouple, 


-19- 


insulated  in  a silica  tube, was  extended  thru  an  opening  in  the  front 
of  the  furnace.  PIG.  7 shows  the  arrangement  of  the  muffle  for 
determining  the  melting  points  of  slags. 

TABUE  II  (A  and  B)  shows  the  composition  of  the  slags  used, 
and  the  calculations  of  their  silicate  degree,  and  melting  points. 

It  was  found  that  Slag  #2  had  a higher  melting  point  than  Slagjfl, 
caused  by  the  removal  of  KgO  from  Slag  #1.  Upon  adding  B2O3  to 
Slag  #2,  the  melting  point  was  considerably  lowered.  Substituting 
GaP  for  KgO  in  Slag  § 1,  increased  the  melting  point  about  20°. 

The  fluidity  was  found  to  increase  upon  the  addition  of  borax  and 
calcium  fluoride,  but  to  decrease  when  EgO  was  present.  Slag  #1 
was  found  to  be  too  viscous  and  Slag  #2  had  too  high  a melting 
point  to  be  used  satisfactorily.  Slag  #4  proved  to  be  quite  suc- 
cessful!, having  a melting  point  about  100°  below  that  of  the  steel, 
and  being  very  fluid  at  the  temperature  of  the  pour. 

Molds:  After  the  solution  of  the  problems  of  obtaining  high 
temperatures,  suitable  slags  and  crucibles  which  would  hold  up,  that 
of  suitable  molds  was  studied.  The  first  molds  tried  were  made  of 
a mixture  of  powdered  fire-clay  and  sand  with  water  as  a binder.  A 
cylindrical  form,  6 z | inches  was  used  in  a vertical  position  into 
which  the  steel  was  poured.  Blow-holes  and  contraction-holes  were 
formed,  however,  and  it  was  believed  that  if  a mold  were  made  with 
the  upper  part  terminating  in  the  shape  of  an  inverted  bell  and 
sufficient  metal  poured  to  fill  this  enlarged  opening,  the  holes 
caused  by  the  contraction  of  the  metal  would  be  eliminated.  (See 
FIG.  8A)  When  this  was  tried,  it  was  found  that  the  blow-holes  were 
formed  as  before.  This  was  not  due  to  a scarcity  of  metal,  but  to 
the  fact  that  the  gases  did  not  have  time  to  escape. 


-20- 


ry*/*'  &/* 


-32- 


TABLE  III  (A) 
CALCULATION  OP  SLAGS 


COMPO- 

SITION 

MOL.  WT. 

AMOUNT 

T 

MOL.  RATIO 

# COMPO- 
SITION 

M.P.  OP 
SUBSTANCE 

SLAG  # 1 

CaO 

56.1  g. 

67.32  g 

1.20 

39.4 

1995°C 

A1203 

102.2 

26.57 

.26 

15.5 

3000 

Si02 

60.4 

59.70 

.99 

35.0 

1750 

Fe203 

159.8 

12.78 

.08 

7.8 

1541 

k2o 

55.0 

2.20 

.04 

1.2 

890 

MgO 

40.3 

2.02 

.05 

1.1 

1900 

SLAG  # 2 

CaO 

56.1 

70.68 

1.26 

45.8 

1995 

AI2O3 

102.2 

26.57 

.26 

17.2 

2000 

S102 

60.4 

42.28 

.70 

27.4 

1750 

PegO  3 

159.8 

12.78 

.08 

8.3 

1541 

MgO 

40.3 

2.02 

.05 

1.3 

1900 

SLAG  # 3 

CaO 

56.1 

70.68 

1.26 

44.8 

1995 

A120  3 

102.2 

26.57 

.26 

16.8 

2000 

SiO  2 

60.4 

42.28 

.70 

26.9 

1750 

Pe203 

159.8 

12.78 

.08 

8.1 

1541 

MgO 

40.3 

2.02 

.’05 

1.2 

1900 

B2°3 

154.0 

3.08 

.02 

2.2 

577 

SLAG  # 4 

CaO 

56.1 

67.32 

1.20 

39.1 

1995 

A1o03 

102.2 

26.57 

.26 

15.4 

2000 

Si02 

60.4 

59.79 

.99 

34.8 

1750 

PGgOg 

159.8 

12.78 

.08 

7.4 

1541 

MgO 

40.3 

2.02 

.05 

1.2 

1900 

CaP2 

78.0 

3.12 

.04 

2.1 

1378 

V . 


-23- 


TABLE  III  - (B) 


SLAG  no. 

M.P. 

OXYGEN  IN  BASE 
” " ACID 

SILICATE  DEGREE 

1 

1320-1330 

230/198  = 1.1/1 

Mono-silicate 

2 

1400-1425 

233/140  = 1.6/1 

Sub-silicate 

3 

1250-1275 

234/143  = 1.63/1 

n n 

4 

1350-1375 

228/198  = l.l/l 

Mono-silicate 

To  eliminate  these  gases,  a mold  was  constructed  as  shown  by 
FIG.  8-B.  The  metal  is  poured  down  a vertical  passage  into  a hori- 
zontal cylindrical  opening,  at  the  other  end  of  which,  a vertical 
passage  was  constructed  for  the  escape  of  gases.  A very  rough  cast- 
ing was  obtained  with  a hollow  space  or  ”pipe”  extending  thruout  its 
length.  In  an  attempt  to  eliminate  the  roughness  of  the  surface,  an 
iron  pipe  1-4  x 12  inches,  closed  at  one  end  was  embedded  in  a sand 
box.  A crucible  from  which  the  bottom  had  been  removed  was  cemented 
onto  this  pipe,  the  purpose  being  to  provide  a bell  into  which  the 
excess  metal  could  be  poured.  This  gave  a smooth,  external  appearance 
but  synmetrically  arranged  blow-holes  appeared  thruout  the  casting, 
and  a '’pipe”  extended  thru  three  inches  of  the  length.  A mold  con- 
structed as  the  one  shown  in  FIG.  8 - C is  recommended.  The  steel  is 
poured  down  one  passage,  passes  thru  a horizontal  passage  and  rises 
Into  the  other  arm,  thus  driving  out  the  gases. 

Altho  about  twenty-five  attempts  were  made  to  obtain  a casting 
free  from  blow-holes  and  of  such  size  that  a test-bar  could  be 


’ 


. 


-24- 


machined  from  it,  the  results  were  entirely  disappointing.  Every 
precaution  was  taken  in  regard  to  the  control  of  temperature  in 
pouring,  the  fluidity  of  the  slag,  the  type  of  mold,  and  the  peiiod 
of  solidification,  hut  hlow-pipes  or  holes  appeared  in  every  case. 

The  failure  of  the  castings  may  he  attributed  to  several  causes: 

First,  the  small  quantity  of  steel,  which  of  necessity  was  used, 
caused  too  rapid  solidification.  This  resulted  in  the  inclusion  of 
the  gases  in  the  pasty  mass  of  the  metal  and  their  retention  hy  the 
metal  on  solidification.  In  the  smaller  furnaces,  about  one  pound 
was  melted,  the  purpose  of  the  small  eastings  being  to  obtain  a 
piece  which  could  be  photographed.  The  enlarged  furnaces  were  capa- 
ble of  holding  a crucible  of  five-pound  capacity,  or  enough  metal  to 
fill  a mold  12  x li  inches.  It  is  suggested  that  an  ingot  three 
inches  in  diameter  and  14  inches  long  be  cast  into  a hot  mold 
(See  FIGr.  8-0)  in  an  attempt  to  eliminate  too  rapid  solidification. 
This  would  require  28.4  pounds  of  steel  and  a crucible  and  furnace 
of  sufficient  size  would  have  to  be  constructed. 

An  analysis  of  the  blow-hole  gase  £22) 

has  shown  that  they  con- 
tain hydrogen,  nitrogen  and  earbon  monoxide.  The  first  two  are 
probably  absorbed  from  the  gases  in  the  combustion  chamber,  while 
the  last -mentioned  gas  is  formed  by  the  action  of  the  carbon  in  the 
steel  upon  the  ferrous  oxide  dissolved  during  the  melt.  This  reac- 
tion may  be  represented  by  the  equation:  C + FeO  — > CO  + Fe.  The 
higher  the  temperature,  the  more  FeO  will  be  dissolved  and  conse- 
quently the  more  CO  will  be  liberated.  The  length  of  time  of  solidi- 
fication, however,  will  be  greater,  and  thus  the  gases  will  have 

022) 

more  time  to  escape.  It  has  been  recommended  that  if  the  metal 
is  stirred  just  before  pouring,  the  escape  of  the  gases  will  be 


■ 


. 


' 

' 

' 

; • ; 


-25- 


hastened. 

It  was  thot  that  by  adding  a sufficient  amount  of  deoxidizing 
material  for  about  twenty  minutes  before  pouring,  the  FeO  would  be 
reduced  so  that  no  CO  would  be  formed.  This  was  tried,  but  the 
small  quantity  of  metal  used  was  probably  responsible  for  the  blow- 
holes produced.  The  problem  of  blow-holes  in  steel  castings  is  one 
which  has  been  a source  of  trouble  and  annoyance  to  the  steel 
industry.  As  one  investigator  expressed  it:^23^  ,TThere  is  no  rapid 
ar  royal  road  to  the  production  of  sound  steel  eastings;  this  is 

<T 

only  accomplished  by  lond  experience  combined  with  specialized 
knowledge " . 

The  vanadium  added  was  in  the  form  of  ferro -vanadium  manufac- 
tured by  the  Standard  Alloy  Company  of  Canonsburg,  Pa.  The  analysis 


presented  by  them  is  as  follows: 

Vanadium 34.70 

Iron 62.17 

Carbon 0.22 

Silicon 2.83 

Phosphorus 0.08 


100.00 

The  weight  of  f erio-vanadium  used  was  34  grams  and  was  placed 
in  2,275  grams  of  steel,  after  the  latter  was  in  a molten  state. 

The  deoxidizer  was  allowed  to  remain  20  minutes  before  the  steel 
was  poured.  The  samples  obtained  were  examined  under  the  microscope 
Numerous  slag  inclusions  were  present  in  the  samples  to  which  the 
deoxidizer  had  not  been  added.  The  samples  to  which  the  agents  had 
been  added  proved  to  be  quite  free  from  slag  inclusions. 


. 

. 


< i 1 L 

' 

Vi  ’ 


-26- 


IV.  SUMMARY 

The  solution  of  the  problem  of  determining  the  effect  which 
certain  deoxidizing  agents  have  on  the  properties  of  steel  castings 
involved  the  preparation  of  several  sound  ingots,  free  from  blow- 
holes, contraction-holes,  and  "pipes" . 

Because  of  the  inadequacy  of  the  furnaces  in  the  laboratory, 
a gas  and  air  blast  furnace  was  devised  v/hich  gave  temperatures  up 
to  1700°  C.,  or  275°  above  the  melting-point  of  the  40-carbon  steel 
used.  The  crucibles  which  were  used  were  made  by  coating  the  outer 
surface  of  graphite  crucibles  with  alundum  cement.  Of  the  various 
slags  used  to  prevent  oxidation  and  to  purify  the  steel  of  inclu- 
sions, the  one  that  was  found  most  satisfactory  contained  constitu- 
ents which  lowered  the  melting-point  to  75°  below  the  melting  point 
of  the  steel.  It  was  also  fluid  enough  to  cause  a complete  separa- 
tion of  the  slag  from  the  steel  during  the  pour.  Suitable  molds 
were  made  of  sand  and  clay  and  constructed  so  as  to  allow  for  the 
escape  of  gases.  Due  to  the  presence  of  blow-holes,  the  tensile 
strength  could  not  be  determined.  The  samples  were  polished  and 
etched  and  inspected  under  the  microscope.  The  slag  inclusions 
in  the  samples  to  which  the  deoxidizer  had  been  added  were  not 
present  to  any  great  extent,  while  many  inclusions  were  found  in 
the  samples  to  which  the  deoxidizer  had  not  been  added.  The  conclu- 
sion was  drawn  that  the  deoxidizing  agents  have  a very  beneficial 
effect  in  removing  slag  and  gas  inclusions  from  steel  castings. 


-27- 

V 

BIBLIOGRAPHY 

1.  Giolitti,  Federico,  "Heat  Treatment  of  Soft  and  Medium  Steels'1, 
pp.  216-242. 

2.  Bessemer,  Henry,  Trans.  A.  I.  M.  E.  22,  : 282. 

3.  Austen,  Roberts,  "Presedential  Address  to  Iron  and  Steel  Insti- 
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of  Oast  Iron  and  Steel,"  Tr.  Am.  Soc.  Mech.  Eng.,  22:570. 

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14.  J.  Frank.  Inst.  184:637. 

15.  Waterhouse,  G.  B. , "Influence  of  Titanium  on  Segregation  in 
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ingens  fOrlag,  p.31  (1920)  


-28- 

17.  Giolitti,  F. , ’’Heat  Treatment  of  Soft  and  Medium  Steel’1,  p.  243. 

18.  Sauveur,  "Metallography  and  Heat  Treatment  of  Iron  and  Steel", 
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